1. Field of the invention
The present invention relates to a golf club head.
2. Description of the Related Art
When hitting a golf ball by a golf club, a backspin is put on the golf ball. A backspin rate exerts a great impact on a carry and trajectory of the golf ball, and hence is desired to be as constant as possible regardless of hitting conditions of the golf ball. This is because if a backspin rate of the golf ball is kept constant regardless of the hitting conditions, it becomes possible for the golf ball to be invariably hit to a target place.
There has been a problem, however, that when a face surface of the golf club head, acting as a contact surface with respect to the golf ball, gets wet due to rainfall or the like, the backspin rate varies significantly. Such variation in backspin rate increases under a wet condition compared to under a dry condition in the case of a driver, but conversely in the case of a wedge it decreases significantly under a wet condition.
Whereas, a plurality of grooves, called score lines, are generally formed on the face surface of the golf club head in a toe-to-heel direction for the sake of stabilizing the backspin rate. The configuration or the like of the score lines, however, is strictly regulated by the rules and therefore there is a limit to suppressing the variations of the backspin rate in rainfall by devising the configuration of the score lines.
In order to solve such problem, it has been proposed to form fine grooves with a width of 200 to 800 μm on a face surface, as disclosed in Japanese unexamined patent application publication No. 2011-234748. As such, it has conventionally been believed that wider grooves formed on the face surface exert a higher water discharging effect than do thinner grooves thereon. It has been learnt by an experiment, however, that even if such comparatively wide fine grooves are formed on the face surface, there cannot be obtained a sufficient effect to prevent the backspin rate from varying in rainfall.